This invention relates generally to means for transporting electrical devices, and in particular to media for the in-process transportation of electrical devices.
As used herein, the term "electrical device" shall refer to and mean semiconductor devices, integrated circuit devices, hybrid devices and the like. As used herein, the term "backend processing" shall refer to and mean all of the heating, cooling, testing, sorting, marking and other processes which an electrical device undergoes from the time it is assembled to the time it is ready for shipment to a customer.
Generally, assembled electrical devices are transported through the various backend processing machines in one of two ways. One is known as "naked" handling, where no type of electrical device protection or handling standardization is used. Here, the devices are fed "as is" to a processing machine from a transport medium known as a tube. One tube generally holds 15 to 30 devices depending on the device size. The devices are stacked in the tubes. A typical tube contains twenty-seven 16-pin, 300 mil devices. Generally, the tubes are made of plastic or aluminum. They do not carry any kind of readable tracking identification indicia and are hand-carried, typically in a box or tote, from process step to process step. The devices must be removed from the tubes for each process step on a per machine basis. When a machine has completed a process step (or steps), the devices are returned back into a tube (probably a different tube) to be carried to the next process step. Information containing the results of the last and all previous process steps is usually recorded by hand on a piece of paper (traveler) and is transported with each group (lot) of tubes.
Such conventional processing technology, therefore, is very labor intensive. In large manufacturing facilities workers are needed to transport the tubes of devices from process step to process step. In fact, manufacturing lot sizes are typically limited to the number of devices that one operator can carry by hand. Many times, the integrity of the results of a process step is dependent on where the operator places a tube of processed devices. Misplacing a tube can easily compromise the integrity of a lot. In addition, information associated with the lot is usually carried on paper with the devices and must be hand entered at each process step by the operator. This requires additional skilled operators and further allows for human error to be introduced.
Other problems with conventional backend processing are associated with loading and unloading the devices in tubes for each process step. Naked handling allows mechanical defects (bent leads, chips, etc.) and electrostatic discharge failures. Bent leads, in turn, can cause the various process machines to jam up.
Further problems are associated with the processing machines themselves. Since each machine must unload and reload the devices into the tubes, each machine must be adapted to a particular device form. Besides the expense of having such device specific machines, such adapted machines are quite prone to failure, (e.g. jams, mis-processing) due to minor fluctuations in device form and wear associated with high volume handling. Furthermore, the electrical devices manufacturer is burdened by having to maintain various pieces of equipment that are dedicated to a particular device package form.
The other method incorporates the use of a "carrier". The devices are placed in a plastic frame to protect the contact leads and to provide limited handling standardization. These carriers, with the devices installed, are also fed to the machines in tubes.
Carriers reduce mechanical defects and reduce package specific handling to some extent. But, carriers still cause jams due to wearing of the relatively soft plastic from which the carriers are made. Furthermore, handling standardization only occurs across common package styles with similar lead counts (i.e., 14-18 lead DIP's or 68-88 lead PGA's).
Backend processing by this invention eliminates the tube. In the preferred embodiment as will be described, the electrical devices, up to 256 of them, are latched into seats defined by a planar tray, the seats being coordinately arranged, such as in a standard X-Y format. The tray is the common transport medium for the devices to and from all processing equipment, and during all processing. Preferably the seats of a tray can be configured to accomodate a wide variety of device package forms, while not changing the outside dimensions of the tray. This standardizes the processing equipment and minimizes their dependence on changing package types.
The devices are loaded into a tray one time and then the tray is used as the transport medium throughout the backend processing. This eliminates the need to handle the devices individually at each process step and thereby standardizes the equipment and greatly improves their reliability. The possibility of damage to the devices is vastly reduced as they are never touched by human hands, and the number of machine insertions are reduced to a minimum because full trays of devices are inserted rather than individual devices. Also, since each device in a tray occupies a unique position in a coordinate system, each device can be uniquely identified at each process step. Thus, the traceability and reliability of device process information is vastly improved over conventional methods.
This invention will allow an electrical device manufacturer to totally automate his or her line with minimal set-up changes to run a wide variety of products. The devices can be automatically conveyed to their appropriate process steps under the direction of a process control system. Then they can be loaded and unloaded using a mechanism such as an automated loading arm. The load arm might consist of an X-Y-Z positioning matrix, or it might be a commercially available robot arm. Lot sizes can be optimized to implement a just-in-time approach to manufacturing. Material queues can be reduced through faster set-up times and line flexibility.
Other advantages and attributes of this invention will be discussed in, or will be readily discernible upon a reading of, the text hereinafter.